The invention relates to an air spring device having an air spring bellows made of elastomer material, an air spring cover and an air spring piston, wherein the air spring bellows which is essentially self-supporting in the operating state is attached in an airtight fashion by its first end the air spring piston so as to form a first rolling fold, and by its second end to the air spring cover so as to form a second (rolling) fold, and together with the air spring cover and the air spring piston forms a hollow chamber with an elastic volume, wherein the air spring device has a sleeve-shaped external guide which surrounds the air spring bellows tangentially, and at least one internal clamping ring which is arranged inside the air spring bellows, wherein the external guide is to be attached in a frictionally and/or positively locking fashion to the external surface of the air spring bellows using the internal clamping ring. The invention also relates to a particularly suitable method for manufacturing an air spring bellows for such an air spring device.
Air spring devices, also referred to for short as air springs, which are clamped between the chassis and vehicle body and which have an air spring bellows which is in turn attached between an air spring cover, for example on the chassis side, and a rolling piston on the vehicle body side are known in a large number of designs. The air spring is subject to an internal excess pressure during operation. The air spring bellows rolls under load and in the case of spring movements so as to form a rolling fold on the external contour of a concentric component, usually on the air spring piston/rolling piston. Such an air spring is frequently used in road vehicles or rail vehicles in order to provide comfortable suspension. The air spring is subject to an internal excess pressure during operation.
In this context, there are both air springs in which the air spring bellows forms a rolling fold only on one side, specifically generally on the rolling piston, or air springs in which the rolling bellows is clamped between an air spring cover and rolling piston so as to form a (rolling) fold on both sides. Air springs with a rolling fold on one side can often be found in passenger cars, while the often larger air springs with a greater load-bearing capacity with rolling folds on both sides tend to be installed in trucks and rail vehicles.
In addition, thin, i.e. thin-walled, rolling bellows are desired to increase a comfortable suspension behavior and to reduce what is referred to as the harshness behavior. A person skilled in the art understands the term harshness to mean a superimposed, somewhat rough, hard suspension behavior when relatively high-frequency and low-amplitude oscillations occur, which arises as a result of the dependencies of the designs, materials, intrinsic damping means, inertia, etc. which are customary with air spring units and shock absorber units.
In order, however, to obtain a sufficient load-bearing capacity of the overall system in relatively thin rolling bellows, the rolling bellows or the air springs or shock absorbers have to be provided with what are referred to as external guides, specifically with a tubular “supporting corset” or supporting body which surrounds the rolling bellows. In this way it is possible to optimize, for example, a thin rolling bellows with a thin lightweight metal tube as a supporting body to high internal pressures and therefore high load-bearing capacities accompanied at the same time by good harshness behavior.
The external guides are arranged in such a way that the rolling bellows can roll both on the outside of the rolling piston and on the internal surface of the external guide.
When spring movements occur, the air spring bellows in air springs with a double fold, as well as in those with just one fold, therefore usually rolls essentially on the external contour of the air spring piston while retaining the rolling fold. In air springs with a double rolling fold or a rolling fold on both sides, a situation in which the rolling fold which is located on the air spring cover rolls on cover components is minimized by corresponding shaping of the cover, or is entirely prevented so that a continuously defined position of the individual elements of the air spring device is ensured.
Those air springs in which the air spring bellows forms a rolling fold only on one side generally have different diameters in the different regions of attachment of the air spring to the air spring cover and to the air spring piston. For example, the air spring bellows of the air spring system disclosed in DE 197 53 637 is attached to an air spring cover having a relatively large diameter, and is attached to a significantly smaller rolling piston in such a way that just one rolling fold is formed. With this design it is easily possible for an external guide in the form of a sleeve which surrounds the air spring bellows and is supported on the outside to be attached to the larger diameter of the air spring cover. The attachment as such can easily be carried out by means of clamping rings on the fixed cover, and the large diameter of the external guide allows sufficient space to form the rolling fold.
However, if the external guide, for example in the case of a double rolling fold, has to be held only by the air spring bellows itself, the attachment becomes rather difficult, in particular if a long service life is required. Although solutions which propose a method of attachment such as bonding or vulcanizing are achievable, they do not always provide the desired durability.
DE 298 23 508 U1 presents such a method of attachment and, in addition to bonding and vulcanizing also discloses the alternatives of crimping or clamping by widening an internal clamping ring. However, due to a lack of more detailed specification, the widening process described in said document should only be considered to be a theoretical possibility for an attachment method. On the one hand, a position which is uniform over the circumference and a sufficient degree of extension of a clamping ring for the purpose of mounting are virtually impossible if a clamping ring is inserted into the air spring bellows when the latter is still in the unloaded state. On the other hand, introducing a clamping ring into an air spring bellows which is already widened under internal pressure has not yet been carried out and is assumed to be feasible only with a very large degree of expenditure.